As is known in the art, future diesel powertrains will likely be equipped with diesel particulate filters (DPF) and lean NOx traps (LNT). The DPF traps soot in the exhaust and needs to be regenerated, i.e. the soot needs to be burned off, every 500 miles or so. This is achieved by elevating the temperature (to around 600 deg C.) and providing enough oxygen to combust the soot. LNTs are poisoned by sulfur in the fuel and oil, and need to be desulfated every 3000 miles or so. This is achieved by elevating the temperature (to around 700 degrees C.) and depleting the exhaust gas of oxygen, i.e. running rich. Heating the exhaust gas and depleting oxygen uses extra fuel, which reflects negatively on the fuel economy.
The inventors have recognized that it would be desirable to coordinate both processes efficiently and to use the synergies to the largest extent possible. This invention proposes such coordination between DPF regeneration and LNT desulfation (deSOx).